A Magnetic Resonance Study of Low Salinity Waterflooding for Enhanced Oil Recovery

Abstract

Low salinity waterflooding (LSF) has been proposed to improve oil recovery, with major projects in progress worldwide. There is however no consensus on the mechanisms of LSF for enhanced oil recovery (EOR). Wettability change is the most widely accepted mechanism. In this work, magnetic resonance (MR) and magnetic resonance imaging (MRI) were employed to monitor oil displacement processes during model laboratory scale LSF experiments. The MR and MRI measurements permit evaluation of putative LSF mechanisms. Two clay-coated sand packs, one with nonswelling kaolinite, the other with swelling montmorillonite, were prepared as model porous media for LSF. The interactions between pore fluids (oil and water) and the clay-coated pore surfaces were evaluated with relaxation time measurements. A MRI methodology, spin echo single point imaging (SE-SPI), was employed to spatially resolve the T 2 distribution along the sand pack. The oil saturation profiles were determined from SE-SPI measurements. A new differential relaxation time distribution method is proposed in this work for oil saturation estimation. The pore fluid self-diffusion coefficients were measured. The mechanism of wettability change for LSF is suggested on the basis of the oil diffusion coefficient variation with LSF. The similarities and differences between the kaolinite and montmorillonite behaviors are discussed. This work demonstrates that MR and MRI are robust tools to monitor oil displacement processes, with the potential to reveal the mechanisms of LSF and other procedures for enhanced oil recovery.

Miscible Fluid Displacement in Rock Cores Evaluated with NMRT2Relaxation Time Measurements

“…All core flooding was performed at a volumetric flow rate of 0.1 ml/min. This flow rate corresponds to a superficial velocity of 3.4×10 -6 m/s in the core, which falls within the range of velocities reported as typical for fluid flow in reservoirs [45][46][47] and is thus essentially comfortably in the creeping flow regime. 48,49 For the case of methane being displaced by the other fluids, the viscosity ratio (M = injected/displaced) is always greater than 1, in which case piston-like displacement is expected.…”

Pore-scale insights into transport and mixing in steady-state two-phase flow in porous media

“…The results of this research provide fresh insights into the potential impact of saturation topology on mixing between the modified salinity water and the formation brine under steady-state flow conditions, which has not been investigated and reported in the literature.Hydrodynamic dispersion and mixing in two-phase flow through porous 2 media are found in many natural, industrial, and engineering processes such 3 as contaminant transport in the vadose zone where the infiltrated water car-4 ries the contaminants and mixes with the resident water, while air has filled 5 some part of the pore space [37,4,23]. Another example is the modified-6 (or low-) salinity water flooding (MSWF) as one of the enhanced oil recovery 7 techniques, in which injection water with a tuned chemical composition is 8 injected into the reservoir filled originally with the formation brine and the 9 crude oil [31, 1,29,42]. The performance of MSWF depends on many pore-10 scale physio-chemical factors such as crude oil chemistry, formation brine and 11 injection water chemistry, temperature, and rock mineralogy, which have 12 been extensively studied [33, 2,25].…”

NMR-Compatible Sample Cell for Gas Hydrate Studies in Porous Media

“…16,17 In order to facilitate such studies at relevant reservoir conditions, the use of a variety of rock core holders which are compatible with NMR/MRI hardware has been reported. [18][19][20][21][22] Located within NMR/MRI magnet systems, these holders are generally required to be constructed from non-metallic materials. In this regard, high-strength polymers (e.g.…”